I always pick up my hulls. If hunting with a double I will catch them and stick them with the dead birds in my game bag. At the end of the day it's fun to see how many shells it took me to get dinner. If I hunt with an auto I still try to pick up the shells but inevitably one always escapes me. For this reason I try to use paper hulls. Paper doesn't last long and I know if I loose a shell it will be gone in a few months.
I wish "they" made paper 16 gauge hulls so I could do the same with my Sweet 16.
My friend never picks up his hulls. His excuse is the wad does more littering than the hull. I feel leaving your hull behind is rude and it is the same as throwing trash out your car window. If I could find my wads I would pick those up too.
Best
Brian